1. Field of the Invention
The present invention relates to an image capture apparatus and a method for controlling the same, and in particular, to image shake correction technique for suppressing image shake caused by a motion of an image capture apparatus, such as camera shake.
2. Description of the Related Art
Conventionally, so-called image shake correction functions are known that correct (mitigate) blurring (image shake) of a captured image caused by a motion of an image capture apparatus, and optical image shake correction and electronic image shake correction are typical methods for realizing image shake correction functions (see Japanese Patent Laid-Open No. 2011-145604). Optical image shake correction is a method for suppressing a motion of an object image by a moving optical member such as a shift lens or an image sensor, based on a detected amount of shake of an image capture apparatus. In addition, electronic image shake correction is a method for suppressing a motion of an object image by setting an area of effective pixels smaller than an area of recordable pixels, and shifting the position of the area of effective pixels based on a detected amount of shake of an image capture apparatus.
In addition, rotational direction components such as yaw, pitch, and roll due to a rotation (a rotational shake) of an image capture apparatus may be included in blurring (image shake) of a captured image caused by a motion of the image capture apparatus, in addition to parallel movement (translational direction) components that are correctable by an image shake correction method described in Japanese Patent Laid-Open No. 2011-145604. Moreover, a technique for correcting image shake due to rotational direction components of a shake by applying a geometric deformation process to a captured image is disclosed in Japanese Patent Laid-Open No. 2008-5084.
For example, it is conceivable that image shake due to rotational direction components of a shake is corrected using the geometric deformation process disclosed in Japanese Patent Laid-Open No. 2008-5084, after correcting image shake due to translational direction components of a shake using the image shake correction technique disclosed in Japanese Patent Laid-Open No. 2011-145604.
In geometric deformation processing of an image as disclosed in Japanese Patent Laid-Open No. 2008-5084, it is necessary to refer to other pixel values in order to generate corrected pixel values. An area made up of the referred pixels is referred to as a reference area. If the necessary reference area is not included in the imaging area (captured image), it is impossible to correctly perform a correction requiring the reference area, and in some cases, a part of the corrected image is missing.
Therefore, if a geometric deformation process is performed on an image that has been subjected to correction of image shake due to translational direction components of a shake, it is possible that a reference area necessary for the geometric deformation process is not included in the imaging area (area of a captured image held in a memory), and that a part of the corrected image is missing.
A case will be described with reference to FIGS. 11A and 11B where a geometric deformation process is performed on an image that has been subjected to correction of image shake due to translational direction components of a shake.
In FIG. 11A, an entire area 1100 is an area of the entire captured image (for example, the entire captured image held in a memory of an image capture apparatus). A reference area 1101 is a reference area necessary for a geometric deformation process for correcting rotational direction components of a shake. In addition, an area 1102 represents the area within the reference area 1101 that is not included in the captured image 1100. An area 1103 represents a rectangular area circumscribing the reference area 1101.
In FIG. 11B, an image 1104 is an image subjected to a geometric deformation process using the reference area 1101. P1 in FIG. 11A represents the center position of an object image, and P2 in FIG. 11B represents a position obtained by converting the pixel at the position of P1 by geometric deformation processing. P2 is located in the center (the point where the diagonals intersect) of the image after geometric deformation.
Conventional optical image shake corrections have not been intended for a geometric deformation process after image shake correction. Because of this, corrections have been performed without regard to the magnitude of rotational direction components of a shake such that an object image and an imaging area of an image sensor maintain a predetermined positional relationship (for example, a state in which the centers of an object image and an imaging area correspond to each other). However, the center of the rectangular area 1103 circumscribing the reference area 1101 that is necessary to correct a distortion generated in an object image due to rotational direction components of a shake such as tilting does not necessarily coincide with the center of an imaging area. Thus, there has been a case where an ability to correct image shake due to rotational direction components of a shake by geometric deformation processing is not effective when capturing an image in an imaging area larger than a record size.
For example, in an example in FIG. 11A, if P1 is shifted in a top right direction, the reference area 1101 (and the rectangular area 1103) is (are) fully contained in the captured image, and no part of the corrected image is missing even if a geometric deformation process making use of the reference area 1101 is performed. However, in conventional optical image shake corrections, since optical members are controlled so that the position of P1 does not change, there has been the area 1102 in which the reference area 1101 is not fully contained in a captured image.